The article How Web Servers and the Internet Work discusses the concept of domain names. "Howstuffworks.com" is a domain name. The com portion of the name is called the top-level domain name. There is a very small set of generic top-level domain names, which you will probably recognize:

• com - for commercial endeavors
• org - for non-profit organizations
• net - for network providers
• mil - for military organizations
• gov - for government organizations
• edu - for educational organizations
  
• info - for entities providing information services

There are also a number of top-level domain names for individual countries, including countries like Canada (ca), Australia (au) and the United Kingdom (uk). IANA, the Internet Assigned Numbers Association, provides world-wide management of the top-level domain names.